I was laid off Nov. 17 and I can tell you it was not lump sum but it's not true payroll either. Here's how it works: You are on payroll until the date they tell you (mine was Dec. 1 so my last true "payroll" check was Dec. 15.) Then my "severance" checks began on Dec. 29. I will get 6 severance checks paid to me every 2 weeks. I got 12 weeks of pay so my last severance check will be March 9. I would not think they would have changed this process after all this time of doing it this way. This is how it's been done for years. Check with HR, because to my knowledge, you would not get 1 lump sum of money.
You should get severance checks paid to you bi-weekly for your term of severance. But...no insurance premiums , 401K or HSA/FSA money is taken out, so the checks are larger than previous paychecks, which helps.
And BTW...you can apply for unemployment on or after your effective termination date that HR gives you (probably Feb. 1). However, you can't start getting unemployment benefits (money) until your severance payouts are complete.